The Commanding Stone by David Forbes

Gerin, King of Khedesh, has long since accepted the mantle of Amber Wizard—the first in a millennium—with all the terrible responsibility that accompanies it. He has prevented the dread wizard-king, Asankaru, from attaining the all-powerful Words of Making, but the enemy grows stronger by the day.

And now Gerin must be resolute and pursue the secret of the Words at any and all cost. For a new foe has emerged in a furious race toward a magical artifact that can awaken and command monsters long thought dead. And nothing will survive the devastation wrought by dragon fire.